This invention relates to a lifting platform.
There are many circumstances in which it is required to lift an object from a low level to a higher one in circumstances where such tools as cranes cannot be used and when the object to be lifted is too heavy, or the distance of lift is too high, for the operation to be carried out manually. One example is lifting luggage or freight to the freight door of an aircraft. Another example is supporting an object such as a petrol engine during overhaul. In both these cases it may be required that the platform carrying the object shall be tilted and it may be required that the angle of the platform in relation to the ground, whether level or tilted, remained constant during the lift. These two uses and many others might be met by the present invention, but in the description that follows reference will be made to a bed such as is now used in a hospital.
It is now usual in hospitals to try to avoid transferring patients from one piece of equipment to another. For example, if a patient is to be transferred from a medical to a surgical ward, it is desired that he shall use the same bed in both wards. It is looked on as desirable to carry the patient from one place to another in his own bed. Nevertheless the present invention is adapted to be used as the basic element of a trolley as well as of a bed. A great deal of ancillary equipment is now used in conjunction with beds in hospitals and provision must be made, if the bed is to be universally adaptable, for the incorporation of such equipment, or at least for the use of accessories in conjunction with the bed.
A hospital bed should be capable of having any height between 450 mm and 750 mm. The lifting of the patient can be accomplished by using an electrical or mechanical linear actuator, or a hydraulic ram.
The present invention has two parts. A bed using the first part would lift the patient vertically and maintain him level at all points of the lift to within the limit that can be felt by the patient or by a nurse. If however the full range of the present invention is to be used so that the patient may be tilted according to the second part with his head up or down compared with a level position, the main support for the bed must be close to a vertical line through the patient's centre of gravity and is preferably so placed that when restraint on tilting is released, the bed with a patient is heavy towards the foot by an amount that a nurse can feel but can easily handle. The range of tilting required is 25.degree. from 10.degree. foot down to 15.degree. foot up, either infinitely adjustable or with step positions that will allow adjustments of approximately 2.degree. to be made. It is desirable that the platform should maintain a level position or any preset angle within the 25.degree. range throughout its vertical movement of 305 mm to within a tolerance of .+-.1.degree..
So that the base of x-ray equipment or of overbed tables may be accommodated, a clearance from the floor to the base (which is assumed to be carried on castors) of 127 mm is required.
Many attempts have been made to produce a design that will meet all these requirements. No practicable proposal is known which will allow the bed to be moved to the limit of tilt when it is in its lowest position and in particular that will allow the foot of the bed to be tilted down when the bed is low.
It is an object of the present invention to provide a lifting platform that will avoid the difficulties heretofore experienced or which will at least afford the public a useful choice.